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Comment by mortenjorck | Hacker News Reader

This is really the worst externality of "flying cars," or whatever you want to call short-range commuter aircraft. In absence of some exotic propulsion technology (what usually powers flying cars in science fiction), the amount of air that must be displaced to loft a vehicle carrying one to four people will always be orders of magnitude louder than a land vehicle.

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Noise was certainly a problem for this proposed inter-city transport:

https://en.wikipedia.org/wiki/Fairey_Rotodyne https://www.youtube.com/watch?v=y9633v6U0wo

Sailplanes carry 2 people and can be launched almost without any noise at all using an electric winch (common in Europe).

If you wanted to use this for commuting, just add a front electric sustainer to it. By the time the sustainer turns on, the aircraft is already pretty high altitude.

It'd be just as quiet as a land vehicle due to the greater distance away from the hearer.

but yeah, helicopters are likely to be fairly loud.

You're not a free flight aviator, are you? I don't mean to be rude, it's just that I've found that people who don't fly things are always much more optimistic and naive about the realities of air travel than actual pilots are. I'm not trying to sound snarky- I had the same level of optimism and bright ideas for the uses of air travel until I got an aerospace engineering degree and started flying hang gliders.

Sailplanes wouldn't work for commuting because of, in order:

1. Difficulty of training 2. Pilot liability for accidents 3. Weather 4. Space required to take off and land

I'm a sailplane, powerplane and a paraglider pilot and experimental airplane owner, with two decades of soaring flight behind. I have a micro-scale meteorology and atmosphere modeling as a hobby. I work as an engineer and computer vision researcher, on autonomous vehicle project.

My expert opinion - for limited delivery applications sailplanes could work. You need to do it right - sample and model atmosphere from the vehicle and ground, use gravity to accelerate and decelerate to flying speed, complete automation to remove the pilot. It's not easy. But it is not impossible.

(Incidentally, if someone is willing to drop me ~500k in an attempt to build a prototype - I might consider investing the time required.)

I agree with you for "limited delivery applications", by if we're talking about limited delivery applications, why wouldn't we just use low-cost powered flight? Much safer and more controllable.

Low cost eVTOL flight? It has high external costs of noise pollution. Also the eVTOL is nessesarily a complicated machine. The cost of that complexity is high.

By talking sailplanes, I didn't mean unpowered flight. Of course you need power, to counteract drag . I was primarily referring to a form-factor (clean, efficient and and silent like a sailplane) and to a mode of takeoff and landing (convert speed to altitude with a wing, instead of eVTOL).

I'm in training to become one. I've flown a sailplane a few times now.

I'm merely pointing out one method that would allow near-elimination of noise.

...and you can fly a sailplane at a younger age (13 for solo flight) than you can drive (usually 16). And driving has most of those concerns as well.

1 could be handled by a full autopilot; perhaps it can make 2 a non-issue; and by planning aircraft landing and take off centrally, 4 could be dealt with as well.

Autonomous car: - drives pretty much on a plane - able to stop when confused - precise speed and direction control - stable (i.e. does not oscillate or slide) - uses the same environment (the actual road) for reference and "handling" (tire grip) - anyone with IQ > 70 can drive one

Autonomous sailplane: - flies in 3D space with pitch, roll, yaw - has both MAX (Vne) and MIN (stall) speed, can't stop and wait - can't even stop descending (!) - HEAVILY influenced by wind and thermal conditions - pretty unstable, oscillates when upset - can not use ground as visual reference reliably - flying one is no joke even for a human, requires serious training

Good luck with your full autopilot.

Autonomous car is harder than autonomous plaine. An autonomous plane can be flown with near-zero accidents by dGPS and traffic control alone. Try that with a car ;) . But take an autonomus plane, add an atmospheric model - you can have an autonomous sailplane.

It can be FLOWN with near zero-accidents by dGPS and control alone. That's steady/level flight, not counting issues with weather, launching, landing, and responding to in-flight emergencies. In a driving failure case, you crash or slow down, and you generally keep the accident constrained to the road. In a flying failure case, you've got a high-speed projectile moving in 3 directions.

Flown = Takeoff, flight, landing, emergencies handling.

What pilots usually do during emergency is to go through the checklist. There is not much room for improvisation.

Vehicles - it is a completely different level of problem. If you try to drive with dGPS alone, you will collide almost immediately. Even on the empty road, because dGPS is not good enough. And actually, it is almost AGI-complete problem, as you need to model and interact with other traffic participants.

> Good luck with your full autopilot.

While it doesn't completely negate your argument...

https://www.raspberrypi.org/blog/zero-hab-glider/

http://izzybrand.com/

If you wanted to use this for commuting, just add a front electric sustainer to it.

How about a solution for a VTOL craft, like the Boeing vehicle? How about an airship with high speed winches, with smaller drones managing the ends of the cables? The cables could attach to aircraft that want to take off, which would be pulled up to a height where their rotor noise wouldn't be so annoying.

This is an interesting idea - and sailplanes can carry a lot more than 2 people :) ex. Waco CG-4 .

That said, they were also nick named "flying coffins".

re: winch tow - when I was an Air Cadet in canada as a teen, we used to fly in schweizer 2-33's and occasionally went up on the winch - it was absolutely exhilarating!

That's a glider, but not really a sailplane...

...I've flown a 2-33. It's not much better than the Waco! :)

Unfortunately, I haven't flown it with a winch.

Helicopters are loud because the blades cross over the airframe and are powered by turbines. An electric multicopter based design could have significantly lower noise levels.

If going by the noise emitted by your average consumer drone, and scaling it up, I think the opposite is probably true - it would be crazy loud.

Consumer drones aren't really aiming for quiet though. My racing drones are very buzzy since the small 3-5in props are fast spinning to have quick reaction time. My heavy lift photography drone with its slow 12in props (aiming for efficiency) is way larger and much quieter.

Few consumer level drones make any effort at noise reduction. Blade and shroud design can significantly impact noise production.

https://www.dronethusiast.com/what-are-the-best-silent-drone...

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